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1 IEEE P Wireless Personal Area Networks Project Title IEEE P Working Group for Wireless Personal Area Networks (WPANs) TG4g Coexistence Assurance Document Date Submitted April 2011 Source Re: [Chin-Sean Sum] [NICT, Japan] *List of co-authors in the document Voice: [ ] Fax: [ ] Abstract Purpose Analysis on coexistence of g with other 802 systems within the same spectrum bands To address the coexistence capability of g Notice This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P

2 Contributors of the CA document are sorted by alphabetical order of the last name: Afshin Amini Phil Beecher James P.K. Trainwreck Gilb Hiroshi Harada Fumihide Kojima Clinton Powell Benjamin A. Rolfe Chin-Sean Sum Khurram Waheed 1. Introduction 1.1. Bibliography [B1] IEEE Std TM 2005, IEEE Standard for Information Technology Telecommunications and Information exchange between systems Local and metropolitan area networks Specific requirements Part 15.1: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Wireless Personal Area Networks (WPANs). [B2] IEEE Std TM 2003, IEEE Recommended Practice for Information Technology Telecommunications and Information exchange between systems Local and metropolitan area networks Specific requirements Part 15.2: Coexistence of Wireless Personal Area Networks with Other Wireless Devices Operating in Unlicensed Frequency Bands. [B3] IEEE Std TM 2003, IEEE Standard for Information Technology Telecommunications and Information exchange between systems Local and metropolitan area networks Specific requirements Part 15.3: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for High Rate Wireless Personal Area Networks (WPANs). [B4] IEEE Std TM 2006, IEEE Standard for Information Technology Telecommunications and Information exchange between systems Local and metropolitan area networks Specific requirements Part 15.4: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (WPANs). [B5] IEEE Std TM 2007, IEEE Standard for Information Technology 2

3 Telecommunications and Information exchange between systems Local and metropolitan area networks Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. [B6] IEEE Std g /D1 2010, IEEE Draft Standard for Information Technology Telecommunications and Information exchange between systems Local and metropolitan area networks Specific requirements Part 15.4: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (WPANs) Amendment 4: Physical Layer Specifications for Low Data Rate Wireless Smart Metering Utility Networks. [B7] IEEE Std n TM, IEEE Standard for Information Technology - Telecommunications and Information exchange between systems - Local and metropolitan area networks - Specific requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications - Amendment 5: Enhancements for Higher Throughput Acronyms ASK AWGN BER BPSK Coex-beacon CA CAP CCI CCK CFP CSM CSMA/CA D-QPSK DSSS DUR ED FER FFD FHSS amplitude shift keying additive white Gaussian noise bit error rate binary phase shift keying coexistence beacon coexistence assurance contention access period co-channel interference complementary code keying contention free period common signaling mode collision avoidance multiple access / collision avoidance differential quadrature phase shift keying direct sequence spread spectrum desired to undesired ratio energy detection frame error rate full function device frequency hopping spread spectrum 3

4 GFSK Gaussian frequency shift keying GTS guaranteed time slot LQI link quality indicator MAC medium access control MPM multi-phy management MR-FSK multi-rate and multi-regional frequency shift keying MR-OFDM multi-rate and multi-regional orthogonal frequency division multiplexing MR-O-QPSK multi-rate and multi-regional offset-quadrature phase shift keying PAN personal area network PHY physical OFDM orthogonal frequency division multiplexing O-QPSK offset-quadrature phase shift keying PSSS parallel sequence spread spectrum QAM quadrature amplitude modulation RF radio frequency RFD reduced function device SC single carrier SFD start frame delimiter SHR synchronization header SINR signal to interference and noise ratio SIR signal to noise ratio SOI sphere of influence SUN smart utility network TDMA time division multiple access 2. Overview 2.1. Overview of IEEE g The IEEE Task Group 4g defines PHY amendment and related MAC extensions based on for wireless Smart Utility Networks (SUN). The objective of the standard is to provide a global standard that facilitates very large scale process control applications such as the utility smart-grid network capable of supporting large, geographically diverse networks with minimal infrastructure, with potentially millions of fixed endpoints. 4

5 An g network contains one centralized coordinator. The coordinator starts and manages the network to facilitate communications among network devices. A network consists of one coordinator and at least one network device. In the g, there are two types of devices, the FFD and the RFD. The FFD contains the complete set of MAC services and is capable of acting as either a coordinator or a network device. The RFD contains reduced set of MAC services and is only capable as a network device. For medium accessing, the devices employ CSMA/CA to avoid wasteful collisions. Alternatively, TDMA may also be employed for guaranteed transmissions. This standard specifies a total of three PHYs, namely the MR-FSK, MR-OFDM and MR-O-QPSK. All the PHYs are specified to address different system demands and market segments. In order to avoid mutual interference caused by multiple PHYs operating in the same location, an MPM scheme is defined to coordinate among the potentially coexisting PHYs. Each PHY is specified to allocate a fraction of regulated spectrum bands out of the complete list shown in the following sub-clause Regulatory Information The allocated frequency bands for the g are given as below: (a) MHz (Worldwide) (b) MHz (United States) (c) MHz (Europe) (d) MHz (Japan) (e) MHz (China) (f) MHz (United States, Canada) (g) MHz (United States) (h) MHz (United States) (i) MHz (United States) (j) MHz (United States) (k) MHz (China) (l) MHz (Korea) Out of the list, bands (a)-(e) and (k) are occupied by more than one g PHY, while bands (f)-(j) and (l) are only occupied by a single PHY. The details are listed in the Table 1. 5

6 Table 1 Regulatory Domains for Respective PHYs Specified in g Frequency Band IEEE g PHYs MR-FSK MR-O-QPSK MR-OFDM MHz (Worldwide) X X X MHz (United States) X X X MHz (Europe) X X X MHz (Japan) X X X MHz (China) X X MHz (United States, Canada) X MHz (United States) X MHz (United States) X MHz (United States) X MHz (United States) X MHz (China) X X X MHz (Korea) X 2.3. Overview of Coexistence Mechanism in and g The importance of coexistence mechanism in the SUN is two-fold. Internally, the SUN specified three alternative PHYs and these PHYs shall be able to coexist with each other if operating co-locatedly in the same frequency band. Externally, the SUN has to share multiple frequency bands with dissimilar 802 systems. The following sub-clauses describe the coexistence mechanism specified in the and g, that facilitates both homogeneous (among different SUN PHYs) and heterogeneous (across other 802 systems) coexistence MPM scheme The MPM scheme is a newly defined mechanism in the g. The motivation of defining the MPM is the specification of multiple alternative SUN PHYs potentially operating in the same frequency bands. The sole objective of MPM is to facilitate CCI avoidance when more than one PHY are occupying the same channel. The description 6

7 of MPM can be found in sub-clause 5.2b [B6]. To facilitate the MPM operation, a pre-defined common PHY mode known as the CSM, a new frame known as the coex-beacon, and several corresponding MAC functions are specified. Coordinators of all three PHYs that operate at duty cycle greater than 1% shall be able to transmit and receive the CSM. The basic operation of the MPM is to require the coordinators to scan for the coex-beacon in CSM. Upon receiving a coex-beacon, the incoming coordinator realizes that there is another network occupying the channel, and may take several measures to avoid CCI, such as trying another channel or achieving synchronization with the current network. On the other hand, while operating in a certain channel, a coordinator is also required to send out coex-beacon in CSM to alert possible incoming coordinators Common Signaling Mode (CSM) The CSM is a pre-defined common PHY mode that has to be supported by all the specified PHYs in g. CSM is used to aid coexistence among the alternative SUN PHYs. The role of the CSM is coexistence is primarily two-fold: (a) to facilitate the MPM mechanism that targets interference avoidance among networks with different PHYs, and (b) to enable a more efficient detection scheme (e.g. scanning, CCA, and etc.) between networks with different PHY designs. The PHY layer specification of the CSM is given in 6.1a [B6] Channel Scan A channel scan is an act of a receiver to detect any signal present in the channel. The channel scan is the basic means for systems to coexist: enabling detection between networks. There are different types of channel scan that give different levels of accuracy and require different levels of radio resources. In the g, the specified channel scan types are ED channel scan, active channel scan, passive channel scan and enhanced CMS channel scan. The following sub-clauses provide the details of the available scan types in the and g. The ED scan, active channel scan and passive channel scan are specified in , while the enhanced CMS channel scan is newly specified in g. 7

8 ED Channel Scan The ED channel scan allows a device to obtain a measure of the peak energy of the RF signal on the channel it is operating. The ED scan could be used by a prospective PAN coordinator to select a channel on which to operate prior to starting a new PAN. Upon detecting an existing PAN in a specific channel, incoming PAN coordinator may avoid colliding with the existing network by switching to another channel, thus enabling coexistence. The details of ED channel scan are given in [B4] Enhanced CSM Channel Scan The enhanced CSM channel scan is newly defined in g, where three alternative PHYs are specified. A common signaling format, namely the CSM, is a PHY mode that has to be supported by all coordinators. Besides the coordinators, all devices may also support the CSM. The enhanced CSM channel scan allows a device to perform the specific sequence detection of the CSM, which is significantly more accurate as compared to energy detection. In cases where a device, the same goes to any device in the other non-sun systems, is capable of receiving the CSM, the enhanced CSM channel scan can be performed for a more efficient coexistence Active Channel Scan An active scan allows a device to locate any coordinator transmitting beacon frames within its radio SOI. This could be used by a prospective PAN coordinator to select a PAN identifier prior to starting a new PAN, or it could be used by a device prior to association. In a logical channel, the device first sends a beacon request command to the possibly existing coordinator. If the coordinator exists, and is operating in a non-beacon-enabled mode, it will send the beacon in the using the CSMA protocol. If the coordinator is operating in a beacon-enabled mode, it will send the beacon in the next scheduled beacon interval. Besides the intended SUN devices, other non-sun devices may also employ the active channel scan and ED scan in order to detect and avoid possible scenarios of interference. Additionally, if the CSM is supported, CSM scan can be performed for increased detection probability. The details of active channel scan are given in [B4]. 8

9 Passive Channel Scan A passive scan, like an active scan, allows a device to locate any coordinator transmitting beacon frames within its radio SOI. One major difference in the passive channel scan is that the beacon request command is not transmitted by the devices. This scan is used to search for coordinators in the radio SOI, participating in the beacon-enabled mode. An existing coordinator, will send periodical beacons and incoming devices will be performing passive scan to receive the beacon. In a similar way, other non-sun devices may also employ the passive channel scan and ED scan in order to detect and avoid possible scenarios of interference. Additionally, if the CSM is supported, CSM scan can be performed for increased detection probability. The details of passive channel scan are given in [B4] Clear Channel Assessment For the non-beacon-enabled network and CAP in the beacon-enabled network, the CSMA/CA mechanism is specified for handling multiple channel access. In the CSMA/CA mechanism, before transmissions of frames, CCA has to be performed to determine the vacancy of the channel. At least one of the following three CCA methods has to be performed in the CCA: ED over a certain threshold, detection of an g signal (e.g. the CSM), or a combination of these methods. Non-SUN devices may participate in the CSMA/CA protocol in a SUN system if it supports any of the CCA methods, so to avoid CCI with co-locating devices. The details of CCA are given in [B4] LQI and ED The LQI measurement is a characterization of the strength and/or quality of a received frame. The measurement may be one of the receiver ED, the SNR estimation, or a combination of both. An example of conducting an LQI evaluation is by using the ED and SNR measurements. Low ED and low SNR values indicate that the receive signal is weak, possibly due to a bad channel or obstruction. High ED and low SNR values indicate that interference in the channel is present. High ED and high SNR naturally mean that the channel is in good condition. By using the LQI-ED-duet, the factors causing a degraded performance can be determined, or at least estimated, with which, responsive actions can be taken to rectify the situation. The details on ED and LQI are given in and [B4]. 9

10 Channel Switching Channel switching can be performed by a coordinator to avoid a channel with degraded quality due to interference or other factors. Upon determining that the channel quality is degraded (e.g. through LQI measurement), a coordinator may cease current transmissions, perform channel scan to find another channel with better quality to be switched to. The capability of channel switching equips the SUN to be able to coexist with other system, even in cases where the signal characteristics of the co-located network cannot be recognized Neighbor Network Capability Neighbor network capability is a scheme facilitating coexistence and interoperability among multiple PHYs in the SUN, as well as between the SUN and other dissimilar systems. In the beacon-enabled network, GTS can be allocated by the coordinator to a particular device to perform guaranteed transmission within the CFP employing the TDMA protocol. Similarly, a device belonging to a dissimilar system that supports the GTS allocation and management protocol can request and obtain GTS in the CFP to perform local communications. In this manner, the dissimilar system is able to form a neighbor network that could achieve synchronization with the existing SUN. The GTS allocation and management protocol is detailed in [B4]. Besides the CFP, inactive portion is also specified in a superframe for the purpose of power saving. The timing information of the active and inactive boundaries is given in the beacon frame. A dissimilar system can take advantage to occupy the inactive portions of the superframe for local communications. The condition for achieving this level of synchronization is the ability to receive and decode the information contained in the SUN beacon frame. The details of the active and inactive portions are given in [B4] Duty Cycle Duty cycle is known as the proportion of the signal duration to the regular interval or period of time. A part of devices specified in g SUN, primarily the 10

11 battery-powered devices operate in a very low duty cycle. While typical network device may operate at duty cycle as low as below 1%, the coordinators may operate at duty cycle of around 10%, as described in E5.4 [B4]. These low duty cycle devices only transmit energy into the air in a short duration in a long interval, and are less likely to cause interference to other co-located networks SFD Detection The SFD is a field indicating the end of the SHR and the start of the frame data. The function of SFD is to determine the timing boundary from which point the receiver extracts the data in the frame. In g, besides timing establishment, SFD is also designed to facilitate the devices to distinguish the standard specification to which the incoming signal is belonging. The SFD detection is employed for differentiating g frame from the d frame. 3. Dissimilar Systems Sharing the Same Frequency Bands with g This clause presents an overview on other 802 systems which occupy the same frequency bands that are also specified for the g. The following sub-clauses present co-locating dissimilar systems with reference to respective frequency bands. The frequency bands of interest are the MHz band, the MHz band, the MHz band, the MHz band, the MHz band and the MHz band. Each frequency band is discussed referring to a table listing all the coexisting systems from other standard specifications. The contents of the tables (in this and the next sub-clause) are formatted as below: (a) Standard specification: the name of the 802 system with which g system is coexisting (b) PHY specification: the PHY design of the above 802 system specification (c) Receiver bandwidth: the receiver bandwidth of the above 802 system specification (d) Transmit power: the transmit power of the above 802 system specification (e) Receiver sensitivity: the receiver sensitivity of the above 802 system specification. (f) Involved g system: the particular PHY in g that is coexisting 11

12 with the above 802 system specification Note: The data rate modes including receiver bandwidth, transmit power and receiver sensitivity listed in the columns of the following tables are only a part of the complete list from the respective standard specifications. These data rate modes are chosen for the purpose of coexistence analysis in this CA document Coexisting Systems in MHz Band (Worldwide) Table 2 shows the list of other 802 systems that are sharing the MHz band with the MR-FSK, MR-O-QPSK and MR-OFDM PHYs in g. Table 2: Dissimilar Systems Coexisting with g Systems within the MHz Band System PHY Specification Involved g System b DSSS CCK g OFDM BPSK n OFDM QPSK FHSS GFSK MR-FSK, MR-O-QPSK, MR-OFDM SC D-QPSK DSSS O-QPSK 12

13 3.2. Coexisting Systems in MHz Band (United States) Table 3 shows the list of other 802 systems that are sharing the MHz band with the MR-FSK, MR-O-QPSK and MR-OFDM PHYs in g. Table 3 : Dissimilar Systems Coexisting with g Systems within the MHz Band System PHY Specification Involved g System DSSS BPSK c DSSS O-QPSK PSSS ASK DSSS BPSK MR-FSK, MR-O-QPSK, MR-OFDM ah Currently in progress, specification not available 3.3. Coexisting Systems in MHz Band (Europe) Table 4 shows the list of other 802 systems that are sharing the MHz band with the MR-FSK, MR-O-QPSK and MR-OFDM PHYs in g. Table 4: Dissimilar Systems Coexisting with g Systems within the MHz Band System PHY Specification Involved g System DSSS BPSK c DSSS O-QPSK PSSS ASK DSSS BPSK MR-FSK, MR-O-QPSK, MR-OFDM 13

14 3.4. Coexisting Systems in MHz Band (Japan) Table 5 shows the list of other 802 systems that are sharing the MHz band with the MR-FSK PHY in g. Table 5: Dissimilar Systems Coexisting with g Systems within the MHz Band System PHY Specification Involved g System d DSSS GFSK DSSS BPSK MR-FSK, MR-O-QPSK, MR-OFDM 3.5. Coexisting Systems in MHz Band (China) Table 6 shows the list of other 802 systems that are sharing the MHz band with the MR-O-QPSK and MR-OFDM PHYs in g. Table 6: Dissimilar Systems Coexisting with g Systems within the MHz Band System PHY Specification Involved g System c DSSS O-QPSK MR-O-QPSK, MR-OFDM 14

15 4. Coexistence Scenario and Analysis 4.1. PHY Modes in the g System Parameters for g PHY Modes Table 7 shows the PHY modes chosen from each of the MR-FSK, MR-OFDM and MR-O-QPSK PHYs and their corresponding parameters. Table 7: Major Parameters of g PHY Modes System PHY Spec. Receiver Bandwidth (khz) Transmit Power (dbm) Receiver Sensitivity (dbm) PHY Mode MR-FSK kbps FSK g MR-OFDM MR-O-QPSK kbps QPSK CC R FEC =1/2 500kbps O-QPSK CC R FEC =1/2 (8,4) DSSS BER/FER Calculations for g PHY modes In this sub-clause, the BER/FER performance corresponding to SINR for the g PHY modes in Table 7 are provided. The parameter SINR is defined as the ratio between the energy in each chip to the noise power spectral density in each chip. SINR (i.e. E c /N 0 ) can be expressed as: E c /N 0 = E b /N log(l m ) + 10 log(r FEC ) - 10 log(l s ) (1) where, E c /N 0 E b /N 0 L m R FEC L s is the chip energy for over noise power spectral density is the bit energy for over noise power spectral density is the modulation level is the FEC coding rate is the spreading factor 15

16 The Matlab source codes for the BER/FER calculations are given in Annex A. The Q function is defined in C [B2]. FER for the g PHY modes can be calculated from the corresponding BER through the relationship: FER = (2) where, L L L L is the average frame size is 250 octets for FSK 50kbps in this standard is 20 octets for OFDM 200kbps in this standard is 20 octets for O-QPSK 500kbps in this standard The BER and FER of g PHY modes are given in Figure Hollow Markers: BER. Solid Markers: FER FSK (50kbps) OFDM (200kbps) O-QPSK (500kbps) BER/FER SINR (db) Figure 1 BER and FER vs. SINR for g PHY Modes 16

17 4.2. Interference Modeling Interference Characteristics The effect of the interfering signal on the desired signal is assumed to be averaged to the bandwidth of the victim system Receiver-based Interference Model As illustrated in Figure 2, victim receiver Rxv (with receive power P Rv and antenna gain G Rv ) receives the desired signal from the victim transmitter Txv (with transmit power P Tv and antenna gain G Tv ) located at distance d D, while an interferer transmitter Txi (with transmit power P Ti and antenna gain G Ti ) is located at distance d U. The ratio between the desired and undesired power present at the victim receiver will be used as the DUR i.e. SIR of the victim system. At Rxv, the power received from Txv, known as P Rv (in db scale) is given as: P Rv = P Tv + G Tv + G Rv - L p (d D ) On the other hand, the power received from Txi, known as P Rv (in db scale) is given as: P Rv = P Ti + G Ti + G Rv - L p (d U ) Here, all antennas are assumed to be omni-directional, thus angle θ can be neglected. Therefore, the ratio between the desired signal power and the interference power is given as: SIR = P Rv / P Rv 17

18 Figure 2 Illustration for the Receiver-based Interference Model Path Loss Model The path loss model used in this document is the outdoor large-zone systems. The typical urban model is employed. The path loss can be expressed as: L p = log 10 f c + ( log 10 h b ) log 10 d log 10 h b a(h m ) where, f c h b h m d is the operating frequency is the height of the coordinator in the network is the height of the device is the distance between coordinator and device, d can either be d D or d U and a(h m ) is the correction factor for the device antenna height given by: a(h m ) = 3.2 [log h m ] MHz Band Coexistence Performance This sub-clause presents the coexistence performance of the systems coexisting in the MHz band. An involving system is set as the victim while all other systems are set as the interferer, in order to understand the impact of the generated interference. All systems including the g systems and other 802 systems in the MHz band are set as the victim in a round-robin manner. 18

19 Parameters for Coexistence Quantification The following sub-clauses present the parameters involved in quantification of coexistence analysis among the participating systems PHY Modes from Each Standard and Related Parameters Table 8 shows the parameters for the PHY modes in each standard that is coexisting within the MHz band. Table 8: Major Parameters of Systems in the MHz Band System PHY Receiver Transmit Receiver PHY Mode Spec. Bandwidth (MHz) Power (dbm) Sensitivity (dbm) b DSSS CCK 11Mbps g OFDM n OFDM BPSK 6Mbps CC R FEC =1/2 QPSK 18Mbps CC R FEC =3/ FHSS GFSK 1Mbps SC DQPSK 22Mbps DSSS O-QPSK 250kbps BER/FER for PHY Modes in Respective 802 Standards In this sub-clause, the BER/FER performance corresponding to SINR for the all the 802 standards within the MHz band are presented. The parameter SINR is defined as the ratio between the energy in each chip to the noise power spectral density in each chip. The SINR and FER can be derived using (1) and (2) respectively. Here, L L is the average frame size is 1024 octets for b DSSS CCK 11Mbps 19

20 L L L L L is 1000 octets for g OFDM 6Mbps is 4096 octets for n OFDM 18Mbps is 1024 octets for FHSS 1Mbps is 1024 octets for SC DQPSK 22Mbps is 22 octets for O-QPSK 250kbps BER for the b DSSS CCK 11Mbps, FHSS 1Mbps, SC DQPSK 22Mbps and O-QPSK 250kbps are given in E [B4]. BER calculations for the g OFDM 6Mbps and n OFDM 18Mbps are given in Matlab source codes in Annex A. The Q function is defined in C [B4]. The BER and FER curves are given in Figure Hollow Markers: BER. Solid Markers: FER 10-2 BER/FER b 11Mbps g 6Mbps n 18Mbps Mbps Mbps kbps SINR (db) Figure 3 BER and FER vs. SINR for 802 Systems in the MHz Band 20

21 Coexistence Simulation Results g FSK 50kbps Mode as Victim Receiver Figure 4 shows the relationship between the FER performance of the g FSK victim receiver corresponding to the distance between the victim receiver to the interferer. The list of interferers is given in Figure Victim receiver - FSK 50kbps FER Interferer: b/g (11/6Mbps) n (18Mbps) (1Mbps) (22Mbps) (250kbps) Interferer-to-Victim Distance (m) Figure 4 Victim FER vs. Distance between Interferer to g FSK Victim Receiver 21

22 g OFDM 200kbps Mode as Victim Receiver Figure 5 shows the relationship between the FER performance of the g OFDM QPSK victim receiver corresponding to the distance between the victim receiver to the interferer. The list of interferers is given in Figure Victim receiver - OFDM 200kbps FER Interferer: b/g (11/6Mbps) n (18Mbps) (1Mbps) (22Mbps) (250kbps) Interferer-to-Victim Distance (m) Figure 5 Victim FER vs. Distance between Interferer to g OFDM Victim Receiver 22

23 g O-QPSK 500kbps Mode as Victim Receiver Figure 6 shows the relationship between the FER performance of the g DSSS O-QPSK victim receiver corresponding to the distance between the victim receiver to the interferer. The list of interferers is given in Figure Victim receiver - DSSS O-QPSK 500kbps FER Interferer: b/g (11/6Mbps) n (18Mbps) (1Mbps) (22Mbps) (250kbps) Interferer-to-Victim Distance (m) Figure 6 Victim FER vs. Distance between Interferer to g O-QPSK Victim Receiver 23

24 PHY Modes as Victim Receivers This sub-clause presents the results setting other 802 systems as the victim and g as the interferer. Figure 7 shows the relationship between the FER performances of the b/g/n victim receivers corresponding to the distance between the victim receivers to the g interferers Vic: Victim. Int: Interferer FER Vic: b, Int: All g Vic: g, Int: All g Vic: n, Int: All g Interferer-to-Victim Distance (m) Figure 7 Victim FER vs. Distance between Interferer to Victim Receivers. All g display nearly similar characteristics as interferers. 24

25 PHY Modes as Victim Receivers This sub-clause presents the results setting other 802 systems as the victim and g as the interferer. Figure 8 shows the relationship between the FER performances of the (including , and ) victim receivers corresponding to the distance between the victim receivers to the g interferers. The list of interferers is given in Figure Vic: Victim. Int: Interferer Vic: , Int: g FSK/OFDM Vic: , Int: g O-QPSK Vic: , Int: All g Vic: , Int: All g FER Interferer-to-Victim Distance (m) Figure 8 Victim FER vs. Distance between Interferer to Victim Receivers. All g display nearly similar characteristics as interferers. 25

26 MHz Band Coexistence Performance This sub-clause presents the coexistence performance of the systems coexisting in the MHz band. An involving system is set as the victim while all other systems are set as the interferer, in order to understand the impact of the generated interference. All systems including the g systems and other 802 systems in the MHz band are set as the victim in a round-robin manner Parameters for Coexistence Quantification The following sub-clauses present the parameters involved in quantification of coexistence analysis among the participating systems PHY Modes from Each Standard and Related Parameters Table 9 shows the parameters for the PHY modes in each standard that is coexisting within the MHz band. Table 9: Major Parameters of Systems in the MHz Band System Receiver Transmit Receiver PHY Bandwidth Power Sensitivity Spec. (MHz) (dbm) (dbm) PHY Mode DSSS BPSK BPSK 40kbps DSSS O-QPSK O-QPSK 250kbps PSSS ASK ASK 250kbps c DSSS BPSK BPSK 40kbps * Currently in progress, specification not available 26

27 BER/FER for PHY Modes in Respective 802 Standards In this sub-clause, the BER/FER performance corresponding to SINR for the all the 802 standards within the MHz band are presented. The parameter SINR is defined as the ratio between the energy in each chip to the noise power spectral density in each chip. The SINR and FER can be derived using (1) and (2) respectively. Here, L L L L is the average frame size is 22 octets for DSSS BPSK 40kbps is 22 octets for O-QPSK 250kbps is 22 octets for PSSS ASK 250kbps BER calculation for DSSS BPSK 40kbps is given in E [B4], with the modification of bit rate R b from 20kbps to 40kbps. BER calculation for DSSS O-QPSK 250kbps is given in E [B4]. BER calculation for PSSS ASK 250kbps is given in E [B4]. The BER and FER curves are given in Figure 9 27

28 10 0 Hollow Markers: BER. Solid Markers: FER 10-2 BER/FER BPSK 40kbps O-QPSK 250kbps ASK 250kbps SINR (db) Figure 9 BER and FER vs. SINR for 802 Systems in the MHz Band Coexistence Simulation Results g PHY Modes as Victim Receivers Figure 10 shows the relationship between the FER performance of the g FSK 50kbps, OFDM 200 kbps and O-QPSK 500kbps victim receivers corresponding to the distance between the victim receivers to the interferer. The list of interferers is given in Figure

29 10 0 Interferer - All PHY Modes FER Victim receiver: g FSK g OFDM g O-QPSK Interferer-to-Victim Distance (m) Figure 10 Victim FER vs. Distance between Interferer to all g Victim Receivers. All PHY modes in Table 9 display nearly similar characteristics as interferers PHY Modes as Victim Receivers This sub-clause presents the results setting other 802 systems as the victim and g as the interferer. Figure 11 shows the relationship between the FER performances of the (three different PHY modes) victim receivers corresponding to the distance between the victim receivers to the g interferers. The list of interferers is given in Figure

30 10 0 Interferer - All g PHY Modes FER Victim receiver: BPSK O-QPSK ASK Interferer-to-Victim Distance (m) Figure 11 Victim FER vs. Distance between Interferer to all Victim Receivers. All g PHY modes in Table 7 display nearly similar characteristics as interferers MHz Band Coexistence Performance This sub-clause presents the coexistence performance of the systems coexisting in the MHz band. An involving system is set as the victim while all other systems are set as the interferer, in order to understand the impact of the generated interference. All systems including the g systems and other 802 systems in the MHz band are set as the victim in a round-robin manner Parameters for Coexistence Quantification The following sub-clauses present the parameters involved in quantification of coexistence analysis among the participating systems PHY Modes from Each Standard and Related Parameters Table 10 shows the parameters for the PHY modes in each standard that is coexisting 30

31 within the MHz band. System c Table 10 : Major Parameters of Systems in the MHz Band Receiver Transmit Receiver PHY Bandwidth Power Sensitivity Spec. (MHz) (dbm) (dbm) PHY Mode DSSS BPSK BPSK 20kbps DSSS O-QPSK O-QPSK 250kbps PSSS ASK ASK 250kbps DSSS BPSK BPSK 20kbps BER/FER for PHY Modes in Respective 802 Standards In this sub-clause, the BER/FER performance corresponding to SINR for the all the 802 standards within the MHz band are presented. The parameter SINR is defined as the ratio between the energy in each chip to the noise power spectral density in each chip. The SINR and FER can be derived using (1) and (2) respectively. Note that the c DSSS BPSK has similar specifications with that in the DSSS BPSK. Here, L L L L is the average frame size is 22 octets for DSSS BPSK 20kbps is 22 octets for O-QPSK 250kbps is 22 octets for PSSS ASK 250kbps BER calculation for DSSS BPSK 20kbps is given in E [B4]. BER calculation for DSSS O-QPSK 250kbps is given in E [B4]. BER calculation for PSSS ASK 250kbps is given in E [B4]. The BER and FER curves are given in Figure

32 10 0 Hollow Markers: BER. Solid Markers: FER 10-2 BER/FER BPSK 20kbps O-QPSK 250kbps ASK 250kbps SINR (db) Figure 12 BER and FER vs. SINR for 802 Systems in the MHz Band 32

33 Coexistence Simulation Results g PHY Modes as Victim Receivers Figure 13 shows the relationship between the FER performance of the g FSK 50kbps, OFDM 200 kbps and O-QPSK 500kbps victim receivers corresponding to the distance between the victim receivers to the interferer. The list of interferers is given in Figure Interferer - All PHY Modes FER Victim receiver: g FSK g OFDM g O-QPSK Interferer-to-Victim Distance (m) Figure 13 Victim FER vs. Distance between Interferer to all g Victim Receivers. All PHY modes in Table 10 display nearly similar characteristics as interferers. 33

34 PHY Modes as Victim Receivers This sub-clause presents the results setting other 802 systems as the victim and g as the interferer. Figure 14 shows the relationship between the FER performances of the (three different PHY modes) victim receivers corresponding to the distance between the victim receivers to the g interferers. The list of interferers is given in Figure Interferer - All g PHY Modes FER Victim receiver: BPSK O-QPSK ASK Interferer-to-Victim Distance (m) Figure 14 Victim FER vs. Distance between Interferer to all Victim Receivers. All g PHY modes in Table 7 display nearly similar characteristics as interferers. 34

35 MHz Band Coexistence Performance This sub-clause presents the coexistence performance of the systems coexisting in the MHz band. An involving system is set as the victim while all other systems are set as the interferer, in order to understand the impact of the generated interference. All systems including the g systems and other 802 systems in the MHz band are set as the victim in a round-robin manner Parameters for Coexistence Quantification The following sub-clauses present the parameters involved in quantification of coexistence analysis among the participating systems PHY Modes from Each Standard and Related Parameters Table 11 shows the parameters for the PHY modes in each standard that is coexisting within the MHz band. System d Table 11 : Major Parameters of Systems in the MHz Band Receiver Transmit Receiver PHY Bandwidth Power Sensitivity PHY Mode Spec. (MHz) (dbm) (dbm) GFSK GFSK 100kbps DSSS BPSK 20kbps BPSK BER/FER for PHY Modes in Respective 802 Standards In this sub-clause, the BER/FER performance corresponding to SINR for the all the 802 standards within the MHz band are presented. The parameter SINR is defined as the ratio between the energy in each chip to the noise power spectral density in each chip. The SINR and FER can be derived using (1) and (2) respectively. Here, L L is 250 octets for d DSSS GFSK 100kbps is 22 octets for d DSSS BPSK 20kbps 35

36 BER calculation for d DSSS GFSK 100kbps is Annex A. BER calculation for d DSSS BPSK 20kbps is given in E [B4]. The BER and FER curves are given in Figure Hollow Markers: BER. Solid Markers: FER 10-2 BER/FER d GFSK 100kbps d BPSK 20kbps SINR (db) Figure 15 BER and FER vs. SINR for 802 Systems in the MHz Band 36

37 Coexistence Simulation Results g PHY Modes as Victim Receivers Figure 16 shows the relationship between the FER performance of the g FSK 50kbps, OFDM 200 kbps and O-QPSK 500kbps victim receivers corresponding to the distance between the victim receivers to the interferer. The list of interferers is given in Figure Vic: Victim. Int: Interferer 10-2 FER Vic: g FSK, Int: d GFSK Vic: g FSK, Int: d BPSK Vic: g OFDM, Int: d GFSK Vic: g OFDM, Int: d BPSK Vic: g O-QPSK, Int: d GFSK Vic: g O-QPSK, Int: d BPSK Interferer-to-Victim Distance (m) Figure 16 Victim FER vs. Distance between Interferer to all g Victim Receivers. 37

38 d PHY Modes as Victim Receivers This sub-clause presents the results setting other 802 systems as the victim and g as the interferer. Figure 17 shows the relationship between the FER performances of the d (two different PHY modes) victim receivers corresponding to the distance between the victim receivers to the g interferers. The list of interferers is given in Figure Interferer - All g PHY Modes FER Victim receiver: d GFSK 100kbps d BPSK 20kbps Interferer-to-Victim Distance (m) Figure 17 Victim FER vs. Distance between Interferer to all d Victim Receivers. All g PHY modes in Table 11 display nearly similar characteristics as interferers. 38

39 MHz Band Coexistence Performance This sub-clause presents the coexistence performance of the systems coexisting in the MHz band. An involving system is set as the victim while all other systems are set as the interferer, in order to understand the impact of the generated interference. All systems including the g systems and other 802 systems in the MHz band are set as the victim in a round-robin manner Parameters for Coexistence Quantification The following sub-clauses present the parameters involved in quantification of coexistence analysis among the participating systems PHY Modes from Each Standard and Related Parameters Table 12 shows the parameters for the PHY modes in each standard that is coexisting within the MHz band. System c Table 12 : Major Parameters of Systems in the MHz Band Receiver Transmit Receiver PHY Bandwidth Power Sensitivity PHY Mode Spec. (MHz) (dbm) (dbm) DSSS O-QPSK 250kbps O-QPSK BER/FER for PHY Modes in Respective 802 Standards In this sub-clause, the BER/FER performance corresponding to SINR for the all the 802 standards within the MHz band are presented. The parameter SINR is defined as the ratio between the energy in each chip to the noise power spectral density in each chip. The SINR and FER can be derived using (1) and (2) respectively. Here, L is 22 octets for c DSSS O-QPSK 250kbps BER calculation for c O-QPSK 250kbps are given in E [B4]. The BER and FER curves are given in Figure

40 10 0 Hollow Markers: BER. Solid Markers: FER 10-2 BER/FER c O-QPSK 250kbps SINR (db) Figure 18 BER and FER vs. SINR for 802 Systems in the MHz Band 40

41 Coexistence Simulation Results g PHY Modes as Victim Receivers Figure 19 shows the relationship between the FER performance of the g FSK 50kbps, OFDM 200 kbps and O-QPSK 500kbps victim receivers corresponding to the distance between the victim receivers to the interferer. The list of interferers is given in Figure Interferer c PHY Mode FER Victim receiver: g FSK and g OFDM g O-QPSK Interferer-to-Victim Distance (m) Figure 19 Victim FER vs. Distance between Interferer to all g Victim Receivers. 41

42 c PHY Modes as Victim Receivers This sub-clause presents the results setting other 802 systems as the victim and g as the interferer. Figure 20 shows the relationship between the FER performances of the c (one PHY mode) victim receivers corresponding to the distance between the victim receivers to the g interferers. The list of interferers is given in the figure Interferer - All g PHY Modes FER Victim receiver: c O-QPSK Interferer-to-Victim Distance (m) Figure 20 Victim FER vs. Distance between Interferer to c Victim Receiver. All g PHY modes in Table 12 display nearly similar characteristics as interferers. 42

43 5. Detailed Coexistence Analysis and Interference Avoidance/Mitigation Techniques 5.1. Channel Alignment The channel alignment among g systems and other 802 systems are summarized in Table 13, Table 14, Table 15, Table 16 and Table 17 for respective bands within which multiple systems are coexisting. By knowing the locations of center frequencies and system bandwidth for different systems, it is possible to identify and occupy channels with the least likelihood to interfere or be interfered by other coexisting systems. The tables show the center frequencies for respective systems, while the system bandwidth can be obtained from Table 7, Table 8, Table 9, Table 10, Table 11 and Table MHz (Worldwide) Table 13 Channel Alignment for Systems in the MHz Band g b g n MR-FSK MR-FSK MR- MR- DSSS OFDM OFDM FHSS SC DSSS (200kHz) (400kHz) O-QPSK OFDM CCK BPSK QPSK GFSK D-QPSK O-QPSK

44

45 MHz (United States) Table 14 Channel Alignment for Systems in the MHz Band g MR-FSK MR-FSK MR- MR- DSSS DSSS (200 khz) (400 khz) O-QPSK OFDM BPSK O-QPSK

46 MHz (Europe) Table 15 Channel Alignment for Systems in the MHz Band g MR-FSK MR-FSK MR- MR- DSSS PSSS DSSS (200 khz) (400 khz) O-QPSK OFDM BPSK ASK O-QPSK MHz (Japan) Table 16 Channel Alignment for Systems in the MHz Band g d MR-FSK MR-FSK MR-FSK MR- MR- BPSK 1mW BPSK 10mW GFSK (200 khz) (400 khz) (600 khz) O-QPSK OFDM DSSS DSSS DSSS

47

48 MHz (China) Table 17 Channel Alignment for Systems in the MHz Band g c MR- MR- O-QPSK MPSK O-QPSK OFDM DSSS DSSS Coexistence with Transmit Power Control The specifications of IEEE draft standard g addresses low data rate, wireless, smart metering utility networks with a key attribute of low power consumption. An effective control of transmit power not only reduces the power consumed for transmit operation by a SUN device but it also helps with coexistence of a SUN device with other devices sharing the same spectrum in conjuction with other key SUN device attributes such as an inherent low duty cycle of operation, possible minimization of air time by communicating only when a coordinated handshake has occurred. Each SUN device can reduce the amount of interference it generates for the other coexisting devices by keeping its transmitted output power at the minimum level needed to achieve reliable communication. A SUN device can implement a simple mechanism of controlling its transmitted power using a measurement of the received coex-beacon power. The plot in Figure 21 shows using Hata s Model (see section 4.2.3) the path loss 48

49 and the received coex-beacon strength as a function of the distance between the coex beacon transmitting coordinator and a receiving SUN device. Rx Coex Beacon Power as a function of distance between a co-ordinator and a SUN Device Path Loss (db) Coex Beacon Power Received (dbm) Distance between Co-ordinator and SUN Device (m) Figure 21 Coex-beacon signal power as a function of the path loss due to inter-device distance The SUN device receiving the coex-beacon can make a measurement of the received coex-beacon signal strength, e.g., using a mechanism such as received signal strength indictor (RSSI), which can also be used by the automatic gain control mechanism for the receiver chain, to estimate the strength of the incident coex-beacon signal say P beacon_rx. The SUN device can then perform a simple calculation to determine the TX power that it should use to communicate with the coordinator transmitting the coex-beacon as follows: Let P tx,max P tx,min P tx,step Maximum allowable TX output power (dbm) Minimum allowable TX output power (dbm) TX power control step size (db) 49